1. Field of the Invention
The present invention relates to a chip-like LC filter, and more particularly, it relates to a chip-like LC filter which is applicable to a noise filter, for example.
2. Description of the Prior Art
In general, a filter device for filtering high frequency noise signals comprises at least one inductance element and at least one capacitor element. For example, U.S. Pat. No. 4,320,364 granted to Sakamoto et al. and issued on Mar. 16, 1982 discloses the structure of such an LC filter treated as one electronic component.
The U.S. Pat. No. 4,320,364 discloses various embodiments, and FIG. 16 thereof concretely shows the structure of a so-called T-type filter circuit formed as a single electronic component comprising one capacitor element and two inductance elements. In this structure, a pair of opposite capacitor electrodes are provided on both major opposite surfaces of a dielectric plate to form a capacitor element. A substantially U-shaped input/output lead line is soldered to one of the electrodes, and both legs thereof are inserted in ferrite bead members respectively. A ground lead line is soldered to the other capacitor electrode.
Such an LC filter is formed as an electronic component having three lead lines in consequence. In order to mount the LC filter on, e.g., a printed circuit board, the three lead lines are inserted in holes provided in the printed circuit board respectively, to be soldered to respective conductive patterns provided on the printed circuit board.
However, the LC filter having the aforementioned structure is so difficult to manufacture that the assembly operation thereof is complicated. Further, since a dielectric plate having a relatively wide major surface is employed, it is difficult to reduce the size of the electronic component, so mounting density on the printed circuit cannot be substantially improved. Further, mounting of the LC filter is complicated since the same is mounted on the printed circuit board by its lead lines. In addition, the LC filter is connected to a ground conductive pattern of the printed circuit board through a ground lead line, whereby undesired inductance components are generated on the ground lead line. Thus, the effect of noise elimination is lowered and excellent filter characteristics cannot be obtained.